It is well known in the prior art that a tube may be hydroformed to a desired complex tubular shape. The tube is placed between a pair of hydroforming dies having cavities which define the desired resultant shape of the tube. Pressurized hydroforming fluid is then introduced into the tube to expand the tube outwardly into the cavities.
It often occurs that the complex shape of the cavities require that the tube be preformed to an approximate shape of the cavities before the tube is placed into the dies. The prior art has recognized that the pre-forming of the tube can be avoided by positioning the tube between the dies and then filling the tube with fluid under a modest pressure so that the dies can then be closed and the pressure of the fluid residing within the dies will provide sufficient internal support to the tube walls to thereby prevent undesired collapse or other injury to the tube as the tube is forced into the cavities by the closing dies. Thus, although the pre-filling of the tube before closing the dies can avoid the necessity for pre-forming the tube, the hydroforming seals can be subjected to increased stress and wear which can cause an increase in machine down time for seal maintenance.
It is also well known that the complexity of the cavities in the hydroforming dies can result in the need to axially feed the tube into the die cavity as the hydroforming pressures are increased to expand the tube outwardly into the conformance with the complex shapes of the die cavity. This axial feeding under high pressure condition can also cause stress and wear on the seals.
In view of the foregoing, it would be desirable to provide further improvements in hydroforming seals and methods in order to achieve further improvements in the reliability of the sealing of the ends of the tubes as well as improved cycle times for the filling of the tube, and the closing of the dies, and the introduction of high pressure fluid and axial feeding of the tube into the complex shape of the dies.
A hydroforming seal and method includes a nozzle for insertion into the tube, the nozzle being a radially expandable O-ring seal for sealing with the bore of the tube, a conical tapered surface for sealing with the bore of the tube, and a radial shoulder for engagement with the end of the tube. The O-ring seal is expanded to seal the tube and pressurized fluid is added sufficient to support the interior of the tube while the dies are closed and the tube is thereby bent and forced into the die cavity without collapse or injury to the tube by the closing dies. The O-ring seal is then contracted to a non-sealing position and the conical tapered surface provides metal-to-metal sealing while the hydroforming pressure is applied to expand the tube outwardly into the die cavities and the end of the tube is axially fed into the die by the engagement of the radial shoulder with the end face of the tube.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.